I plan to buy Blackberry Pearl 9105 from Middle East, but would like to know if it will work with Mobilcity in Toronto, Canada. I have seen that there are two models of Pearl 9105 which are RCV72UW and RCX72UW and seems they both have bit differnces in the network they support.

I'm with Wind Mobile myself, and Mobilicity and Wind use the same technologies, it looks like. And they are both completely compatible with T-Mobile in the USA. They even tell you that if you can get a T-Mobile phone, you're good go in Canada with these two providers.

The two models of Pearl you mentioned are completely identical in the GSM frequencies. But they have some differences in the UMTS bands, which is the important band that you need for Mobilicity. According to the table above, you need to have compatibility with at least UMTS 1700MHz (UMTS Band IV). So it seems the version of the phone that you plan on getting, RCV72UW, won't work here, since the 1700MHz band is one that's missing on it.